A variety of manually actuable air pumps have been devised particularly for use with bicycles.
A large number of these air pumps use a portion of the bicycle frame as the pump housing and chamber. The major advantage provided by most if not all of these pumps is that they permit manual operation of the pump without having to remove the pump from the bicycle. In many cases, the seat is coupled with an arm of the pump carrying the pump piston to permit reciprocation of the piston operating the pump.
These types of pumps also suffer from several disadvantages. First, the pump is not removable from the bicycle itself since the frame forms a portion of the pump. Second, in many cases such pumps include components which are mounted within the frame members that are thereafter brazed or welded together making subsequent access to the components for repair difficult or impossible without adversely affecting the frame or the finish of the bike. Third, the tubing used in most, though not necessarily all bicycle frames tends to be rather thin and of average commercial quality. Such tubing is weakened and subject to corrosion in areas where it is penetrated, for example to provide air pump fittings.
A lesser number of air pumps designed for use with bicycles include separate pump housings which may be removed from a bicycle frame internally receiving the pump. The major disadvantage of such pumps is that, in all cases known, they must be removed from the bicycle frame to permit operation.
Another major disadvantage of all known, manually operated air pumps is their limited pressure capability. Virtually all such pumps use for piston sealing, a flexible diaphragm having an outer circumferential portion which is formed to permit air to pass when a partial suction is created within the pump chamber and to prevent blowby when air is being compressed in the pump chamber. However, this design has a maximum pressure capability of about 100 psi or less before compressed air blowby will occur.